Mould and Air Quality (LTB)
Residential Indoor Air Quality Guideline: Moulds
Causes of mould growth
Mould growth in a house requires the presence of nutrients, an adequate temperature, and a sufficient amount of water. The first two requirements being usually met in indoor environments, fungal growth usually results from a moisture problem (CMHC 2003). Major causes of mould growth are:
- condensation of moisture on surfaces due to excessive humidity, lack of ventilation, or low temperature;
- water leakage, e.g. from a broken pipe;
- infiltration of water from the outside, e.g. from a leaking roof or a cracked basement; and
- a flood.
Health effects
Health Canada has carried out two reviews of the scientific literature pertaining to the health effects of indoor moulds (Health Canada 1995; 2004). The Institut national de santé publique du Québec also published a review on this subject (d'Halewyn et al. 2003). The following conclusions were drawn:
- exposure to indoor mould is associated with an increased prevalence of asthma-related symptoms such as chronic wheezing, irritation symptoms, and non-specific symptoms; and
- in laboratory animal studies, instillation of fungal antigens (Penicillium sp. and Aspergillus sp.) and fungal cell components [(1->3)-ß-D-glucan] resulted in an inflammatory response in the lungs of rodents, while instillation of Stachybotrys chartarum spores resulted in severe histological and biochemical changes.
These conclusions have been supported by more recent findings. In two cohort studies (Wickman et al. 2003; Jaakkola et al. 2005), significant associations were found between home dampness and the risk of developing asthma. In experimental studies, asthma-like responses were observed in mice following exposure to a typical building-associated fungus, Penicillium chrysogenum (Chung et al. 2005), and inflammatory responses were seen in rats exposed to low doses of toxins from the same species (Rand et al. 2005).
